The invention relates to a safety belt retractor, especially in vehicles, with a belt shaft as a carrier for the belt that is wound thereon as well as a vehicle sensitive and/or belt sensitive controllable block device for the belt shaft, and with a force limiting device, effective in the event of a block event, that is comprised of a viscous medium-filled housing with at least one fixedly positioned contour and a counter-contour that is rotatably displaceable in response to a block event, so that the relative movement between the contour and the counter-contour forces the medium between the surfaces arranged for this purpose.
A safety belt retractor with the above-described features is described in WO 01/58728 A1. With respect to this known belt retractor, the cylindrical housing of the force limiting device is connected to the outer side of the belt retractor housing and is coupled with the belt shaft or, respectively, in particular, with a torsion rod. In one embodiment, in the housing of the force limiting device that is filled with a viscous medium that is, in particular, silicone, there is arranged a succession of fixedly positioned disks between which the ring pistons, configured to dampen the belt shaft or, respectively, to dampen the torsion rod via their rotational movement, grip, with a piston blade radially spaced from its respective ring piston, the disks. During relative movement between the ring pistons and the disks, the silicone is forced between the ring pistons so that the targeted force consumption and, consequently, the force limitation, occurs.
With the known safety belt retractor or, respectively, its force limitation, there is, independent of the respective constructive configuration relative to that described in WO 01/58728 A1, a disadvantage in that its force limitation device cannot be selectively adjusted to different passenger parameters. While it is known that such liquid dampeners react to different crash impulses with a variation of the applied limitation force, a response tailored to the different masses of individual passengers has heretofore not been possible. Accordingly, it is desirable, with respect to large, heavy passengers, to adjustably set the limitation force to a high limit to prevent, for example, in the event of an inflation of an airbag built into the vehicle, a blow to the airbag and, thus, a corresponding risk of injury to the passengers. In the event, on the other hand, that a smaller, lighter person is buckled in with the safety belt, the limitation forces can be adjustably set to lower limits.